Electrode for electrolytic plating and electrolytic plating apparatus including the same

ABSTRACT

Disclosed are an electrode for electrolytic plating and an electrolytic plating apparatus including the same. A contact area between a surface of an object to be plated and an electrode can be minimized using an electrode for electrolytic plating having a non-conductive pattern partially formed thereon. Generation of a metal composite having multiple cores due to simultaneous contact between plural objects to be plated and the conductive region being not covered with non-conductive pattern can be prevented. Since the surface of the object to be plated can be coated with different kinds of metals before galvanic corrosion occurs, a metal composite having a core-shell structure can have improved reliability, quality and stability. Various different kinds of metals can be coated onto the surface of the object to be plated without limitation as the object to be plated.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2014-0039418, filed on Apr. 2, 2014, entitled “ELECTRODE FOR ELECTROLYTIC PLATING AND ELECTROLYTIC PLATING APPARATUS INCLUDING THE SAME”, which is hereby incorporated by reference in its entirety into this application.

BACKGROUND

1. Technical Field

The present invention relates to an electrode for electrolytic plating and an electrolytic plating apparatus including the same, and more particularly, to an electrode for electrolytic plating having a non-conductive pattern partially formed on a surface of a conductive material and an electrolytic plating apparatus including the same.

2. Description of the Related Art

The present invention relates to an electrode for electrolytic plating and an electrolytic plating apparatus including the same, wherein the electrode and the apparatus are used to form a metal composite having a core-shell structure by coating a surface of metal powder with different kinds of metals.

A metal composite having a core-shell structure or a metal powder material formed of a metal composite may be applied to various fields such as conductive pastes for electronic packaging, solar batteries, mobile electronic devices and the like and electromagnetic shielding pastes for blocking electromagnetic waves from electronic devices.

Technical development for improving price competitiveness, reliability, quality and stability of metal composites has been continuously required in the related art.

In general, a method for forming a metal composite having a core-shell structure may include electroless plating or galvanic displacement reaction.

Electroless plating means displacement plating, contact plating, non-catalytic chemical plating or catalytic chemical plating. Typically, electroless plating means catalytic chemical plating, in which metal ions in a metal salt aqueous solution are autocatalytically reduced by a reducing agent without receiving electric energy and the metal is deposited on a surface of an object to be plated. However, the process of forming a core-shell composite by electroless plating has problems such that reaction conditions for forming a core portion and a shell portion with different kinds of metals must be strictly set and various reducing agents and chelating agents are used, thereby generating waste water and increasing manufacture costs.

Galvanic displacement reaction is a voluntary reaction which occurs by a potential difference between two metals. If a potential difference is generated between a metal to be plated and different kinds of metal ions in a solution, the metal to be plated is dissolved into an ion state in the solution and different metal ions in the solution are reduced and coated onto the surface of the metal to be plated.

Electroless plating and galvanic displacement reaction are competitive reactions that can occur at the same time under the same conditions. Therefore, if a thickness of a shell portion corresponding to a coating layer of a metal powder is relatively large or proper reaction conditions cannot be found on a reaction scale, there is a very high possibility of pore generation in the composite (see FIG. 1). As shown in FIG. 2, use of the composite having a core-shell structure with pores therein as an electronic material can cause quality deterioration, such as blistering, low conductivity, solvent absorption, and the like.

Electrolytic plating is suggested to solve such problems of electroless plating and galvanic displacement reaction. However, a typical electrolytic plating apparatus has a problem in that plural metal powders are likely to be coated together and aggregated, instead of being individually coated.

Such an aggregated composite has two or more cores like peanuts instead of a single core, which can increase a possibility of pore generation in the aggregated composite and thus cause quality deterioration, such as blistering, low conductivity, solvent absorption, and the like.

Korean Patent Laid-open Publication Nos. 1998-079372 and 2004-0072704 disclose a plating treatment method and plating treatment apparatus using the same. However, these documents do not provide innovative ways to solve the aforementioned technical issues.

BRIEF SUMMARY

For a long time, the present inventors have tried to develop a plating method and a plating electrode to improve reliability, quality and stability of a metal composite having a core-shell structure formed by various methods known in the art, and finally developed a plating method capable of improving reliability, quality and stability of a metal composite having a core-shell structure and a plating electrode applicable to the plating method.

It is one aspect of the present invention to provide a plating electrode for use in a plating method capable of improving reliability, quality and stability of a metal composite having a core-shell structure.

It is another aspect of the present invention to provide a plating apparatus including a plating electrode capable of improving reliability, quality and stability of a metal composite having a core-shell structure.

In accordance with one aspect of the present invention, an electrode for electrolytic plating includes: a non-conductive pattern partially formed on a surface of a conductive material, wherein an exposed surface of the conductive material being not covered with non-conductive pattern is brought into contact with an object to be plated so as to achieve plating on a surface of the object to be plated.

The exposed surface of the conductive material being not covered with non-conductive pattern may be prevented from simultaneously contacting plural objects to be plated.

The exposed surface of the conductive material being not covered with non-conductive pattern may be formed in a mesh or opening shape having a size 0.5-2 times a diameter of the object to be plated.

The conductive material may be an electroconductive metal.

The electroconductive metal may include at least one selected from the group consisting of Ag, Au, Al, Ni, Cu, and Pt.

The conductive material may have at least one shape selected from the group consisting of a sheet shape, a wire shape, a disc shape, a rod shape, and a foil shape.

The non-conductive pattern may have at least one shape selected from the group consisting of a mesh shape, a stripe shape, a spiral shape, and a spherical shape.

The non-conductive pattern may be an embossed pattern.

The non-conductive pattern may be formed by coating at least one material selected from the group consisting of non-conductive metallic oxide, methylpentenepolymer, polyamide, polytetrafluoroethylene, polyethylene, polypropylene, polyisoprene, polyurethane, polycarbonate, polyimide, polystyrene, polysulfone, polyvinylchloride, and polyvinylidene chloride.

A ratio of a total area of non-conductive regions generated by the non-conductive pattern formed on the surface of the conductive material to a total area of conductive regions being not covered with non-conductive pattern may be 20:80 to 95:5.

The conductive material may have engraved regions formed on the surface thereof, and the non-conductive pattern may be formed by coating a non-conductive material on the engraved regions.

The object to be plated may be a metal powder.

In accordance with another aspect of the present invention, an electrolytic plating apparatus includes: a reaction chamber; an electrode for electrolytic plating disposed in the reaction chamber; and a power source for applying voltage to the electrode for electrolytic plating.

The reaction chamber may include an agitation unit.

The reaction chamber may be a cylindrical barrel and the electrode for electrolytic plating may be disposed along an inner peripheral surface of the cylindrical barrel type reaction chamber.

As described above, embodiments of the invention provide an electrode for electrolytic plating and an electrolytic plating apparatus including the same, in which a contact area between a surface of an object to be plated and an electrode can be minimized using an electrode for electrolytic plating having a non-conductive pattern partially formed thereon. Accordingly, generation of a metal composite having multiple cores due to simultaneous contact between plural objects to be plated and the conductive region being not covered with non-conductive pattern can be prevented.

Further, since the surface of the object to be plated can be coated with different kinds of metals before galvanic corrosion occurs, the metal composite having a core-shell structure can have improved reliability, quality and stability.

In addition, various different kinds of metals can be coated onto the surface of the object to be plated without limitation as the object to be plated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the present invention will become apparent from the detailed description of the following embodiments in conjunction with the accompanying drawings, in which:

FIG. 1 is a view showing a process in which pores are generated in a metal composite having a core-shell structure manufactured by electroless plating or galvanic displacement reaction;

FIG. 2 is an SEM picture of a metal composite having a core-shell structure manufactured by electroless plating or galvanic displacement reaction;

FIGS. 3 and 4 are views showing an electrode for electrolytic plating having a non-conductive pattern partially formed on a surface of a conductive material according to an embodiment of the present invention;

FIGS. 5 to 8 are sectional views of an electrode for electrolytic plating according to an embodiment of the present invention; and

FIG. 9 is a view of an electrolytic plating apparatus according to one embodiment of the present invention.

DETAILED DESCRIPTION

All terms and words used herein should not be construed as limited to common or lexical definitions and should be interpreted as having definitions and concepts corresponding to the spirit and scope of the present invention based on the principle that inventors may pertinently define concepts of the terms in order to describe their own disclosures in the best way. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless context clearly indicates otherwise.

Hereinafter, an electrode for electrolytic plating and an electrolytic plating apparatus including the same according to embodiments of the invention will be described in detail with reference to the accompanying drawings. It should be understood that the present invention is not limited to the following embodiments and may be embodied in different ways.

In accordance with one aspect of the present invention, an electrode for electrolytic plating includes a non-conductive pattern partially formed on a surface of a conductive material in which the exposed surface of the conductive material being not covered with non-conductive pattern is brought into contact with an object to be plated, when plating on a surface of the object to be plated.

According to one embodiment, the exposed surface of the conductive material being not covered with non-conductive pattern may be prevented from simultaneously contacting plural objects to be plated. The object to be plated may directly contact a conductive region and ions of different kinds of metals contained in a plating solution are reduced to form a coating layer as a shell portion on the surface.

Since the non-conductive pattern is partially formed on the surface of the conductive material, the surface of the conductive material being not covered with non-conductive pattern (i.e. a surface not covered with the non-conductive pattern) may be exposed in the form of a mesh or opening. The mesh or opening-shaped surface of the conductive material not covered with the non-conductive pattern does not always need to be formed in an engraved shape.

In the specification, although the mesh or opening may be variously referred to as a region of the surface of the conductive material being not covered with non-conductive pattern, a region not covered with the non-conductive pattern, a surface of the conductive material exposed between the non-conductive patterns, or a conductive region, all these terms have the same meaning. This will be more clearly understood throughout the accompanying drawings.

The surface of the conductive material not covered with the non-conductive pattern and exposed in the form of a mesh or opening is brought into contact an object to be plated, whereby a coating layer can be formed on the surface of the object to be plated.

Herein, the surface of the conductive material exposed in the form of a mesh or opening does not simultaneously contact plural objects to be plated, and the size of the mesh or opening is limited such that the respective objects to be plated individually contact the exposed surface.

In other words, if plural objects to be plated simultaneously contact the conductive region, this can cause cohesion of a composite as the plural objects to be plated are coated at the same time, which results in generation of a metal composite having multiple cores. Since such a metal composite having multiple cores has an uneven structure and shape, it is impossible to obtain a metal composite having a uniform properties, and thus reliability, quality and stability of a metal composite cannot be guaranteed.

Therefore, an object of the present invention is to minimize a contact area between the surface of the object to be plated and the electrode made of the conductive material using the electrode for electrolytic plating having a non-conductive pattern partially formed thereon. Such an object can be achieved by adjusting the size of the non-conductive pattern so as to prevent plural objects to be plated from simultaneously contacting the exposed surface of the conductive material being not covered with non-conductive pattern.

As a result, the size of the non-conductive pattern may be adjusted to determine a desirable size of the conductive region which is the exposed surface of the conductive material being not covered with non-conductive pattern. This can achieve a coating process by allowing a single object to be plated to contact the conductive region being not covered with non-conductive pattern, thereby preventing generation of a metal composite having multiple cores due to simultaneous contact of the conductive region with plural objects to be plated.

As described above, since the non-conductive pattern is partially formed on the surface of the conductive material, the surface of the conductive material not covered with the non-conductive pattern may be exposed in the form of a mesh or opening.

According to one embodiment, the size of the mesh or opening of the exposed surface of the conductive material being not covered with non-conductive pattern may be 0.5 to 2 times the diameter of the object to be plated.

The object (core) to be plated used to form a core-shell composite preferably has a micrometer scale, but is not limited thereto. Therefore, the conductive region which is the exposed surface of the conductive material being not covered with non-conductive pattern, i.e. the mesh or opening, also preferably has a micrometer scale, but is not limited thereto. The size of the mesh or opening of the exposed surface of the conductive material being not covered with non-conductive pattern is preferably 0.5 to 2 times, more preferably 0.5 to 1.5 times the diameter of the object to be plated.

In other words, the size of the non-conductive pattern and/or the mesh size or opening size of the conductive region which is the exposed surface of the conductive material being not covered with non-conductive pattern may vary according to the size of the object to be plated used to form a core-shell composite. Preferably, the size is determined so as to achieve a coating process by allowing only a single object to be plated to contact the conductive region being not covered with non-conductive pattern.

According to one embodiment, the conductive material may include at least one selected from the group consisting of electroconductive metals, for example, Ag, Au, Al, Ni, Cu, and Pt, and may have at least one shape selected from the group consisting of a sheet shape, a wire shape, a disc shape, a rod shape, and a foil shape, without being limited thereto.

Accordingly, since the kind and shape of the conductive material can be variously adjusted and changed according to the purpose and condition of use of the electrode for electrolytic plating according to the embodiment of the present invention, various different kinds of metals can be coated onto the surface of the object to be plated without limitation as the object to be plated.

Herein, the kind and shape of the object to be plated can be variously adjusted and changed according to the purpose and condition of use of the electrode for electrolytic plating according to the embodiment of the present invention. Specifically, the shape of the object to be plated may be non-restrictively selected from the group consisting of a powder shape, a sheet shape, a wire shape, a disc shape, a rod shape, and a foil shape, and is preferably a spherical powder shape.

In general, an electrode for electrolytic plating is disposed in a reaction chamber of an electrolytic plating apparatus. Voltage having a constant magnitude is applied to the electrode from a power source, whereby constant current flows to the electrode.

As described above, the present invention is characterized in that a non-conductive pattern, i.e. an insulation pattern, is partially formed on the surface of the conductive material. Therefore, current generated by voltage having a constant magnitude applied to the conductive material from the power source may be restrictively supplied to an object to be plated, which contacts the exposed surface of the conductive material being not covered with non-conductive pattern, i.e. the conductive region.

According to one embodiment, the non-conductive pattern may have at least one shape selected from the group consisting of a mesh shape, a stripe shape, a spiral shape, and a spherical shape. However, the shape may be variously adjusted and changed according to the purpose and condition of use of the electrode for electrolytic plating. The non-conductive pattern may be formed by coating at least one material selected from the group consisting of a non-conductive material and/or an insulation material, for example, non-conductive metallic oxide, methylpentenepolymer, polyamide, polytetrafluoroethylene, polyethylene, polypropylene, polyisoprene, polyurethane, polycarbonate, polyimide, polystyrene, polysulfone, polyvinylchloride, and polyvinylidene chloride.

Referring to FIG. 3, which shows an electrode for electrolytic plating having a non-conductive pattern partially formed on a surface of a conductive material according to one embodiment of the present invention, the electrode may have a structure in which a non-conductive pattern 302 is coated onto a surface of a conductive material 301 having a wire shape and thus the exposed surface of the conductive material being not covered with non-conductive pattern, i.e. a conductive region 303, is formed in a spherical shape.

Referring to FIG. 4, the plating electrode may also have a structure in which a non-conductive pattern 403 is coated in a mesh (net) shape on a surface of a conductive material 401 having a wire shape and thus a conductive region 402 being not covered with non-conductive pattern is formed in a quadrilateral shape.

Herein, the conductive region is distinguished from a conductive through-hole typically formed in an electrode for electrolytic plating for smooth circulation of a plating solution. In other words, the conductive region is not a part through which the plating solution passes, but refers to the exposed surface of the conductive material being not covered with non-conductive pattern.

By allowing the object to be plated to directly contact the conductive region which is the exposed surface of the conductive material being not covered with non-conductive pattern, ions of the different kinds of metals contained in the plating solution are reduced and form a shell portion on the surface of the object to be plated.

For example, if the object to be plated is a metal powder, ions of the different kinds of metals contained in the plating solution are reduced and form a shell portion on the surface of the metal powder, thereby forming a composite having a core-shell structure.

The mesh size or opening size of the conductive region on the surface of the conductive material being not covered with non-conductive pattern, more particularly, the mesh size or opening size of a portion 303 or 402 of the conductive material exposed between the non-conductive patterns is determined by the size of the object to be plated. Preferably, the mesh or opening has a size that can prevent plural objects to be plated from simultaneously contacting a single mesh or opening. Therefore, the mesh size or opening size is preferably 0.5 to 2 times the diameter of the metal powder which is the object to be plated. For example, if the diameter of the metal powder which is the object to be plated is 20 μm, the mesh size or opening size of a part of the conductive material exposed between the non-conductive patterns may be 10 to 40 μm, preferably 10 to 30 μm.

The present invention is characterized in that the non-conductive pattern, i.e. the insulation pattern, is partially formed on the surface of the conductive material. Therefore, current generated by voltage having a constant magnitude applied to the conductive material from the power source may be restrictively supplied to the object to be plated, which contacts the conductive region being not covered with non-conductive pattern, preferably, to a micrometer scale metal powder.

According to the present invention, by partially forming the non-conductive pattern on the surface of the conductive material, contact between the conductive region and the micrometer scale metal powder can be minimized, thereby preventing generation of a metal composite having multiple cores which may be formed due to simultaneous coating of plural metal powders.

In one embodiment, a ratio of the total area of the non-conductive regions generated by the non-conductive pattern formed on the surface of the conductive material to the total area of the conductive regions being not covered with non-conductive pattern may be 20:80 to 95:5.

As described above, the present invention has a purpose of minimizing contact between the conductive region and the metal powder having a micro-unit size by partially forming the non-conductive pattern on the surface of the conductive material. However, if the ratio of the conductive regions is less than 5%, coating efficiency on the surface of the object to be plated is abruptly decreased. Therefore, this is not appropriate to manufacture a core-shell composite. On the other hand, if the ratio of the conductive regions exceeds 80%, there is a high probability that plural metal powders are coated simultaneously. Therefore, it becomes meaningless to partially form the non-conductive pattern on the conductive material.

Further, as described above, since the non-conductive pattern is partially formed on the surface of the conductive material, the surface of the conductive material being not covered with non-conductive pattern, i.e., the surface not covered with the non-conductive pattern, may be exposed in the form of a mesh or opening.

Referring to FIG. 5 showing a sectional view of the electrode for electrolytic plating according to an embodiment of the present invention, a non-conductive pattern 501 partially formed on a surface of a conductive material 502 may be embossed. The conductive material is exposed at the bottom of the engraved region defined by the embossed non-conductive pattern 501, and the exposed conductive material is subjected to contact with the object to be plated.

Although FIG. 5 shows that the exposed surface of the conductive material 502 not covered with the non-conductive pattern has a planar shape, the exposed surface may be formed in a convex or concave shape.

Referring to FIG. 6 showing a sectional view of an electrode for electrolytic plating according to another embodiment of the present invention, a non-conductive pattern 601 partially formed on a surface of a conductive material 602 may be embossed. The conductive material is exposed at the bottom of the engraved region defined by the embossed non-conductive pattern 601, and the exposed conductive material contacts the object to be plated.

Different from the electrode for electrolytic plating shown in FIG. 5, the electrode for electrolytic plating shown in FIG. 6 is structured such that the conductive material 602 has its own engraved regions formed on the surface thereof and the non-conductive pattern 601 formed by coating a non-conductive material on the engraved regions may be higher than the embossed regions of the conductive material 602.

In FIG. 6, the exposed surface of the conductive material 602 not covered with the non-conductive pattern may be formed in a convex or concave shape as well as a planar shape.

Referring to FIG. 7, which is a sectional view of an electrode for electrolytic plating according to a further embodiment of the present invention, a conductive material 702 has engraved regions formed on a surface thereof and a non-conductive pattern 701 formed by coating a non-conductive material onto the engraved regions may have the same height as that of part or embossed regions 703 of the conductive material 702. Accordingly, the embossed regions 703 of the conductive material 702 are exposed and contact an object to be plated. Herein, the part or the embossed regions 703 of the conductive material 702 may be a concave surface.

Referring to FIG. 8, which is a sectional view of an electrode for electrolytic plating according to yet another embodiment of the present invention, a conductive material 802 has own engraved regions formed on a surface thereof and a non-conductive pattern 801 formed by coating a non-conductive material onto the engraved regions may have the same height as that of part or embossed regions 803 of the conductive material 802. Accordingly, the embossed regions 803 of the conductive material 802 are exposed and contact an object to be plated. Different from the electrode for electrolytic plating shown in FIG. 7, the part or the embossed regions 803 of the conductive material 802 may be a convex surface.

In accordance with another aspect of the present invention, there is provided an electrolytic plating apparatus, which includes a reaction chamber 901, an electrode for electrolytic plating 902 disposed in the reaction chamber, and a power source for applying voltage to the electrode for electrolytic plating. Herein, the electrode for electrolytic plating 902 is characterized in that a non-conductive pattern is partially formed on a surface of a conductive material so as to expose only a part 903 of the conductive material.

Referring to FIG. 9, which show an electrolytic plating apparatus according to one embodiment of the invention, the reaction chamber 901 may include an agitation unit 904. The agitation unit 904 functions to mix an object to be plated with a plating solution.

In one embodiment of the invention, the reaction chamber 901 may be a cylindrical barrel, but is not limited thereto. The reaction chamber 901 may have other shapes, such as a spherical shape or the like, suitable for constructing the electrolytic plating apparatus.

In one embodiment of the invention, the electrode for electrolytic plating may be disposed along an inner peripheral surface of the cylindrical barrel type reaction chamber. In another embodiment, the electrode for electrolytic plating may be additionally provided to the agitation unit 904. With this structure, the agitation unit may have a function of the electrode for electrolytic plating as well as a function of mixing an object to be plated with a plating solution.

Although some embodiments have been described herein, it should be understood by those skilled in the art that these embodiments are given by way of illustration only, and that various modifications, variations, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be limited only by the accompanying claims and equivalents thereof. 

What is claimed is:
 1. An electrode for electrolytic plating comprising: a non-conductive pattern partially formed on a surface of a conductive material, wherein an exposed surface of the conductive material being not covered with non-conductive pattern is brought into contact with an object to be plated so as to achieve plating on a surface of the object to be plated.
 2. The electrode for electrolytic plating according to claim 1, wherein the exposed surface of the conductive material being not covered with non-conductive pattern is prevented from simultaneously contacting plural objects to be plated.
 3. The electrode for electrolytic plating according to claim 1, wherein the exposed surface of the conductive material being not covered with non-conductive pattern is formed in a mesh or opening shape having a size 0.5 to 2 times a diameter of the object to be plated.
 4. The electrode for electrolytic plating according to claim 1, wherein the conductive material is an electroconductive metal.
 5. The electrode for electrolytic plating according to claim 4, wherein the electroconductive metal comprises at least one selected from the group consisting of Ag, Au, Al, Ni, Cu, and Pt.
 6. The electrode for electrolytic plating according to claim 1, wherein the conductive material has at least one shape selected from the group consisting of a sheet shape, a wire shape, a disc shape, a rod shape, and a foil shape.
 7. The electrode for electrolytic plating according to claim 1, wherein the non-conductive pattern has at least one shape selected from the group consisting of a mesh shape, a stripe shape, a spiral shape, and a spherical shape.
 8. The electrode for electrolytic plating according to claim 1, wherein the non-conductive pattern is an embossed pattern.
 9. The electrode for electrolytic plating according to claim 1, wherein the non-conductive pattern is formed by coating at least one material selected from the group consisting of non-conductive metallic oxide, methylpentene polymer, polyamide, polytetrafluoroethylene, polyethylene, polypropylene, polyisoprene, polyurethane, polycarbonate, polyimide, polystyrene, polysulfone, polyvinylchloride, and polyvinylidene chloride.
 10. The electrode for electrolytic plating according to claim 1, wherein a ratio of a total area of non-conductive regions generated by the non-conductive pattern formed on the surface of the conductive material to a total area of conductive regions being not covered with non-conductive pattern is 20:80 to 95:5.
 11. The electrode for electrolytic plating according to claim 1, wherein the conductive material has engraved regions formed on the surface thereof, and the non-conductive pattern is formed by coating a non-conductive material on the engraved regions.
 12. The electrode for electrolytic plating according to claim 1, wherein the object to be plated is a metal powder.
 13. An electrolytic plating apparatus comprising: a reaction chamber; an electrode for electrolytic plating according to claim 1, the electrode for electrolytic planting being disposed in the reaction chamber; and a power source for applying voltage to the electrode for electrolytic plating.
 14. The electrolytic plating apparatus according to claim 13, wherein the reaction chamber includes an agitation unit.
 15. The electrolytic plating apparatus according to claim 13, wherein the reaction chamber is a cylindrical barrel, and the electrode for electrolytic plating is disposed along an inner peripheral surface of the cylindrical barrel type reaction chamber. 